Tie rods system for swimming pools with hopper bottoms

ABSTRACT

This invention pertains to swimming pools and in particular to those swimming pools made with substantially straight sidewalls disposed to generally retain a flexible liner. These sidewalls are usually restrained against outward thrust by tie rods or straps extending from one side to the other when the swimming pool configuration is other than round. These tie rods or straps prevent the sidewalls from moving outwardly from the side thrust of the water pressure in the pool. In the present invention these tie bars or straps for holding the two sidewalls in their erected and spaced condition are disposed to extend from one side to an opposite side while conforming to a hopper contour and with each retained in a depressed condition at its mid-points by means of a pressure pad of determined size which utilizes the weight of the water within the pool to apply a downward force sufficient to keep the pad and the restrained straps from lifting.

United States Patent [191 Hall 1 TIE RODS SYSTEM FOR SWIMMING POOLS WITH HOPPER BOTTOMS [76] Inventor: Raymond L. Hall, 19 Hamilton Court, Whippany, NJ. 07981 [22] Filed: Feb. 17, 1972 [21] Appl. No.: 227,123

Primary Examiner-David J. Williamowsky Assistant Examiner-Philip C. Kannan Attorney-Ralph R. Roberts 1March 13, 1973 [57] ABSTRACT This invention pertains to swimming pools and in particular to those swimming pools made with substantially straight sidewalls disposed to generally retain a flexible liner. These sidewalls are usually restrained against outward thrust by tie rods or straps extending from one side to the other when the swimming pool configuration is other than round. These tie rods or straps prevent the sidewalls from moving outwardly from the side thrust of the water pressure in the pool. in the present invention these tie bars or straps for holding the two sidewalls in their erected and spaced condition are disposed to extend from one side to an opposite side while conforming to a hopper contour and with each retained'in a depressed condition at its mid-points by means of a pressure pad of determined size which utilizes the weight of the water within the pool to apply a downward force sufficient to keep the pad and the restrained straps'from lifting.

12 Claims, 7 Drawing Figures TIE RODS SYSTEM FOR SWIMMING POOLS WITH HOPPER BOTTOMS BACKGROUND OF THE INVENTION 1. Field of the Invention Referring now in particular to the classification of art as established in the US. Patent Office the present invention relates to the general class entitled, Baths,

Closets, Sinks and Spittoons and more particularly to lo the subclass therein of swimming or bathing tank or pool and more particularly to the further subclass thereunder of prefabricated wall sections.

2. Description of the Prior Art Above ground swimming pools have in the last few years become quite popular because of their low cost and ease of construction. These pools generally have sidewalls which are about four feet in height and are made in many shapes and configurations. A very popular shape or configuration of these pools is a pool having a rectangular configuration and those generally rectangular and having rounded ends. In general a round pool having a hopper bottom which provides a depth greater than the nominal four foot has its sidewalls designed so as to be retained by the equal thrust of the water against all the sidewall portions of the round pool. This design generally requires little or no bottom support or the need for tie rods extending from one sidewall to the opposite sidewall. Round pools have several disadvantages among which is the room required for installation which is not always the most practical or available. In particular, the rectangular configuration or configurations of generally rectangular shape having rounded or formed ends other than straight are becoming quite popular as they allow a greater extent for swimming and for the placing of decks on and around the pool rim which permits more people to use the pool. In the construction of these rectangular or semi-rectangular pools it is generally required or desired that the side thrust of retained water against the long sides of the pool is at least in part controlled by means of rods or straps disposed underneath the bottom liner of the pool. These straps or rods are connected from one side to the opposite side to restrain the sidewalls of the pool from bulging outwardly. When the water is in the pool these straps are brought into tension and each becomes very taut, therefore, prior to this invention any attempt to bend and retain these straps out of their normal straight line plane has been a quite complex operation. In general, the forming of a hopper bottom in a pool has required the displacement of the straps from their normal straight line as they extend straight across the pool from sidewall to sidewall. This rearrangement of the rods usually assumes all kinds of diagonal configurations beginning at one side and extending to a midportion of a connected adjacent side. These diagonal arrangements of the straps or rods, or the additional buttressing of the sidewalls, are both expensive, time consuming and often result in unsatisfactory constructions and assemblies.

Hopper bottoms for round pools as conventionally provided are shown in my US. Pat. No. 3,317,926 as issued on May 9, 1967. These pools usually require no tie rods since the thrust against the sidewall is equally accommodated by the sidewall construction as it is placed in tension. In my US. Pat. No. 3,534,414 as issued on Oct. 20, 1970 tie rods are connected from the sides to the end frame members to provide an unobstructed area for a hopper bottom. In U.S. Pat. No. 3,600,722 to SIMSBURY on Aug. 24, 1971 the walls, without the use of tie rods, are built to withstand the side pressure of the enclosed water. An elaborate base and bottom construction avoiding tie rods is shown in U.S. Pat. No. 3,231,902 to RACINA as issued on Feb. 1, 1966. These patents and others using tie rods extending from one sidewall to the other have required elaborate methods for retaining the sidewalls, which methods are not required in the present invention.

The present invention, by means of a simple pressure pad of determinedsize provides means for retaining transverse rods or straps which have been bent out of their normal straight across plane and into the desired configuration to lie adjacent to or just below the liner support surface for a hopper bottom. These bent rods or straps are retained in this installed condition while still supplying the necessary tension or force against the side thrust of the pool. The provision and placement of a pressure pad of a determined size positioned in retaining condition or upon the top of the strap or rod holds the straps in their placed condition. The pressure pad is retained in this positioned condition against the upward pull of the tensioned' rods by means of the downward water pressure exerted on the pad.

SUMMARY OF THE INVENTION This invention may be summarized at least in part with reference to its objects.

It is an object of this invention to provide, and it does provide, means wherein the bottom of the swimming pool is contoured to provide a hopper bottom while below the surface of said bottom there is disposed tie rods extending between the sidewalls of the swimming pool by which the sidewalls are retained against the side thrust of fluid in the pool as retained by a flexible liner.

It is a further object of this invention to provide, and it does provide, an inexpensive means for tying two opposite sidewalls of an above ground swimming pool to each other by means of a strap or rod, which rod or strap is bent out of a straight plane or line to a contour which is below the surface or at the surface of a hopper bottom, said rods or straps being maintained in this contoured condition by means of a pressure pad of determined size which engages the rods at their midpoint and utilizes the downward weight of the water in the swimming pool to retain the pad and engage the rods or straps in their determined configuration.

The sidewall swimming pool tie rod supports of this invention are very simply contoured and require only that the rods be bent to the desired configuration to lie at or below the surface of the hopper bottom and that at the lowermost point and substantially midway of the rods or straps a pressure pad of determined size is laid upon or otherwise attached to the rod to keep the rods in'their originally placed condition so that after water is placed within the swimming pool the water pressure exerted upon the pressure pad retains the rods and pressure in this desired and initially constructed condition.

In addition to the above summary the following disclosure is detailed to insure adequacy and aid in understanding of the invention. This disclosure, however,

is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how it may later be disguised by variations in form or additions of further improvements. For this reason there has been chosen a specific embodiment of a swimming pool with a hopper bottom in which the cross tie straps or rods are contoured to lie below the surface of the hopper and showing a preferred means for holding these straps in place by means of a pressure pad. This specific embodiment and modifications thereof have been chosen for the purposes of illustration and description as shown in the accompanying drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 represents a somewhat diagrammatic plan view of a typical rectangular pool having a hopper portion formed at one end, said hopper portion having straps both longitudinally and laterally depressed to the midpoint of the hopper with a pressure pad retaining the straps at their installed condition;

FIG. 2 represents an end view of the pool frame of FIG. 1, with the view taken on the line 2-2 and looking in the direction of the arrows;

FIG. 3 represents a side view of the pool of FIG. 1 with the view taken on the line 3-3 and looking in the direction of the arrows;

FIG. 4 represents a diagrammatic plan view of a somewhat rectangular pool like that of FIG. 1 but with this pool having semi-circular ends;

FIG. 5 represents a somewhat diagrammatic side view showing the general arrangement of the pool of FIG. 4 with its hopper bottom with the support rods and pads adjacent and below the hopper surface;

FIG. 6 represents a fragmentary plan view of a canal type structure which may be a swimming pool or which may be a long body of water having sidewalls and a liner wall and bottom with the bottom depressed at its midpoint and having tie rods and pressure pads below this bottom contour, and

FIG. 7 represents an end view taken on the line 7'-7 of FIG. 6.

In the following description and in the claims various details will be identified by specific names for convenience. These names, however, are intended to be generic in their application. Corresponding reference characters refer to like members throughout the several figures of the drawing.

The drawing accompanying, and forming part of, this specification discloses certain details of construction for the purpose of explanation of the broader aspects of the invention, but it should be understood that structural details may be modified without departure from the concept and principles of the invention and that the invention may be incorporated in other structural forms than those shown.

DESCRIPTION OFTHE EMBODIMENT OF FIGS. 1-3

Referring now in particular to the embodiment of FIGS. 1, 2 and 3 there is diagrammatically represented a rectangular pool generally indicated as 10 whose frame includes sidewall members 12 and 13 which are of typical construction. To the frame walls are attached plates adapted to retain a flexible liner mounted thereagainst. Gusseted supports 14 are disposed at substantially equal positions along the side frames and the end walls of the pool. The comers are connected in the usual manner to retain the sidewall or a method such as is disclosed in may U.S. Pat. No. 3,534,444 aboveidentified may be employed. In this invention the side thrust of the load of water carried in the pool is intended to be accommodated in a large part by straps of rods extending from one sidewall to an opposite sidewall of the pool. The sides and bottom of the pool are disposed to permit a flexible liner to be laid on a bottom support surface which may be sand or the like with the liner extending up the sides to retain the water. As seen in this embodiment, transverse straps 16 extend from sidewall 12 to the opposite sidewall 13 with one of the straps being identified as 16a. This strap is contemplated to be the mid-strap whereat the slope of the bottom hopper begins. Longitudinal strap 18 extends from end wall 20 to end wall 21 at or slightly below the contoured bottom of the pool.

When and where the strap 18 reaches the midpoint of the pool at support strap it (the strap) is directed downwardly at until it reaches the full depth of the hopper construction and to a point below the liner depth for the hopper bottom provided in this pool. At the extreme bottom extent of the strap at 18b the strap is bent to a flat length which when installed, lies in a plane generally parallel to the top of the pool. This length extends rightwardly and then is upwardly bent at section 180 to be attached to the end wall member 21. Strap 16b is attached to sidewall 12 and then is directed downwardly until it reaches a bottom limit whereat it is bent to form a bottom straight portion 160 which extends for a determined extent to point 16d where it is again bent upwardly toward and to the sidewall 13. The lateral extents 16c and 18b are equivalent to the size of a hold-down support plate 25 which, as shown, is a rectangular plate made of aluminum, scrap metal, covered wood or the like. The size of this plate is determined by the depth of the pool at the sidewall and at the hopper bottom. This depth contemplates that the downward pressure of the water above the plate at the hopper bottom when impressed on this plate is sufficient to retain the side thrust of the pool which must be accommodated by the strap at the point where the strap 16 joins the sidewalls 12 and 13. This side thrust when transferred to the strap tries to pull the strap straight which tends to lift the strap which is retained in position by the downward force applied to the plate.

A support plate 28 is disposed below straps 16a and 18a and provides a support for the strap 18a to prevent its downward movement as it is urged downwardly toward a straight line from end wall 20 to plate 25 as the tension is developed between the end members 20 and 21.

EMBODIMENT OF FIGS. 4 AND 5 Referring next to the pool depicted in FIGS. 4 and 5 it is to be noted that this pool is generally indicated as 30 and has relatively straight sidewalls 32 and 33 with gusset supports 14 disposed at the ends and intermediate portions of said sidewalls. The ends of the pool instead of being straight as in FIG. 1 are made semi-circular and are identified as 35 and 36. These curved end members, having a constant radius, allow the outward thrust forces to be equally distributed requiring no auxiliary base tension members. However, the sidewalls 32 and 33 to prevent bulging must be tied one to the other by tie rods or straps 16, 38 and 39 or use other retention means. These means include driven stakes or posts, massive' sidewalls or heavy beams, all of these means being expensive or requiring more or less permanent installation. It is contemplated that a long sloped hopper, indicated in dashed outline as 40, will be provided and surfaced by the dirt or sand forming the support for the liner. Below this surface tie rod 38 is directed downwardly toward and to a pressure plate or pad 42. These plates or pads are of a predetermined sufficient size or area to utilize the downward pressure exerted by the water in the pool to retain the straps 38 and 39 in their installed condition and prevent the straps from being lifted upwardly in response to the developed thrust against the sidewalls 32 and 33 of the filled pool.

EMBODIMENT OF FIGS. 6 AND 7 Referringfinally to FIGS. 6 and 7 it is to be noted that this same. hold-down concept may be used in a canal or longitudinal trough 60 which may have any type of end configuration. This canal may also extend from one body of water to another and as a canal or trough have its center portion deepened to provide a passageway for a boat, or the like. As shown, the sidewalls of this canal 60 are identified as 62 and 63. Side gussets or supports 14 are provided for these sidewalls and are used as supports in the manner above described for the embodiments of FIGS. 1 and 4. Between sidewalls 62 and 63 are disposed rods or straps 65. These rods have like or substantially like downwardly directed portions identified as 65a and 65b. The midportion of the strap is formed to provide a section which in its installed condition is parallel to the top of the sides or the water in the trough, said section being identified as 65c and upon this section is deposited or attached a pressure plate or pad 67.

Use and Operation of Support Rods for Pools and Canals Having a Depressed or Hopper Portion Referring now to the pools and canals as seen in FIGS. 1, 4 and 6 and the associated FIGS. therewith, it is to be noted that to use tie rods or straps across the bottom of a pool or canal to restrain the side frames against the thrust of the water is a normal and inexpensive method. When the portion between the sidewalls is deepened to provide a hopper or a deepened channel, other measures have been employed such as using concrete or metal posts sunk into the ground. Other means such as heavy beams are also known and used to support the sidewalls of the frame. In many cases the wall support includes mounting the rods in a diagonal pattern to remove the presence of any rods across this hopper portion. This diagonal arrangement, such as seen in FIG. 2 of my U.S. Pat. No. 3,534,414 above noted, is expensive and often is less than satisfactory. This invention permits the rod or strap to be directed downwardly at an angle such as 30 or 45 degrees to the level of the pool and then to or under a pressure holddown plate or pad at the lowermost point.

This plate is made of a determined area so that the plate is held down and retained by the weight of the water in the pool. For example, anticipating a sixteen foot wide pool having a sidewall depth of approximately four feet and an additional three and one-half foot deep hopper will require the straps or rods 16a and 16b to be disposed downwardly toward the center at an angle of about 30 degrees. A structural plate 35 is made 36 inches square and with a depth of water of 7% feet above the plate at this point would provide a water pressure of 3% pounds per sq. inch on the plate or a total of 4200 pounds downward pressure. The lengthwise rod stress against the outer push or thrust of water at the sidewalls and restrained by said rods at 30 degrees results in an upward resultant force which is less than this downward pressure. The rods or strap portions 16b and 16d whose upward thrust are less than the downward pressure on the pad are thus retained in their determined initially deposited condition while the side thrust load on the sides of the pool is mainly retained by these straps. At the mid-length of strap 16a as seen in FIG. 11 it is, of course, necessary that the strap 180 be not pulled downwardly where it crosses underneath the tie strap 16a hence a support pad 28, which is much less in size than the bottom pad structure pad 25, is disposed so as to accept the downward pull of the strap 18a and prevent the strap from cutting into the dirt as it is tensioned by the pull exerted by the water in the pool against the end walls 20 and 21-. This pad 28 is positioned below the strap 18 and 18a and prevents this strap from moving downwardly while pad or plate 25 is placed above straps 18a and to prevent the straps from lifting.

In the use of pads 28, 25, 41, 42 and 67 it is, of course, to be noted that the pads may be positioned above or below the straps or rods as desired by the installer of the pool. For example, pads 25, 41, 42 and 67 may be installed below the rods if appropriate clips are provided to fixedly attach the straps to the plates so that the upward developed force on the rods is offset by the downward thrust or force exerted on the plate. In like manner support plates 28 instead of being below the strap may be positioned above the strap if attached -to it by clips and the like. When'so attached it is only necessary that the downward force be supported by the plate.

Whether rods, straps or other structural configurations are used it is contemplated that they be disposed below the liner forming the water retaining surface of the pool. These rods are attached to the sidewalls or end walls to retain the wall against outward displacement by the sideward thrust of the water in the pool. The method of connection or attachment is merely a matter of selection. The plates forming the pads may be of any material having a sufficient strength to accept the per square inch load of the water and having the necessary resistance to the environment so as to withstand the condition of being buried in dirt, sand and thelike. The plates may be square, round, rectangular or even the straps may be widened so as to become a long rectangular member, just so long as the downward pressure of the enclosed water is sufficient to keep the strap from lifting when and as the thrust of the retained water is applied to the sidewall of the pool.

Terms such as left," right," up," down," bottom," "top," front, back, in," out," and the like are applicable to the embodiments shown and described in conjunction with the drawing. These terms are merely for the purposes of description and do not necessarily apply to the position in which the rods or straps as used for swimming pool sidewall supports may be constructed or used.

While a particular embodiment of the hopper configurations and swimming pools in combination therewith and alternate embodiments have been shown and described it is to be understood that the invention is not limited thereto and protection is sought to the broadest extent the prior art allows.

What is claimed is:

l. A system for retaining the sidewalls of a swimming pool and the like against the outward thrust of contained water of a determined depth in the pool in which the restraining is by members such as tie rods, straps and the like, said restraining members extending from one sidewall to an opposite sidewall and below a liner member forming at least the water retaining means for the bottom of the pool distinguished by having at least a depressed area, said system including: (a) at least one restraining member extending from one sidewall to an opposite sidewall and below at least a portion of the bottom which has been contoured to extend downwardly below the sidewalls to form a hopper, trough, channel and the like, said restraining member being below the liner and at no less than the contoured bottom surface, and (b) at least one hold-down plate secured to the restraining member at substantially its lowermost point, said hold-down plate being made a determined size and oriented so that the weight of the water in the pool and above said plate is utilized to maintain the plate and the restraining member in its installed condition and against the upwardly resultant forces developed in the retaining member as it retains the sidewalls against outward thrust.

2. A system for restraining the opposite sidewalls of a pool as in claim 1 in which said pool is formed with at least two substantially straight opposite sidewalls and the bottom is formed with a hopper and with at least one of the restraining members extending across the pool at and below the liner supporting surface of said contoured hopper with each of attaching lengths of said restraining member being directed downwardly in a substantially straight line from the sidewalls of the pool to its engagement with the hold-down plate.

3. A system for restraining the opposite sidewalls of a pool as in claim 2 in which the hold-down plate is disposed above and in engagement with the lowermost portion of the restraining member.

4. A system for restraining the opposite sidewalls of a pool as in claim 2 in which the pool has four sides and there are at least two restraining members each passing below the hopper and with the planes of each restraining member being disposed at substantially ninety degrees to each other, each member being retained by the same hold-down plate against upward lifting.

5. A tie rod apparatus for retaining the sidewalls of a water retaining structure such as swimming pools, canals and the like, said structures having a contoured bottom extending at least in part below the sidewalls and disposed to support a flexible liner for retaining the water in the structure, said system including: (a) at least one tie rod attached to and extending from one substantially straight sidewall to an opposite straight sidewall, said tie rod layingin a plane which is substantially normal to the top sur ace of the water when in the structure, said tie rod directed downwardly from both sidewalls and arranged to lay below the flexible liner and the contour of the bottom on which the liner rests, and (b) at least one hold-down plate secured to said tie rod at substantially its lowermost point, said hold-down plate being made of a determined size and oriented so that the weight of the water in the pool and on said liner above said plate is utilized to maintain said plate and the tie rod in its installed condition and against the upwardly resultant forces developed in the tie rod as it retains the sidewalls against the outward thrust load of water against the sidewalls.

6. A tie rod apparatus for restraining sidewalls as in claim 5 in which those tie rods extending from one sidewall to an opposite sidewall and which lay in a plane passing through a depressed area in the bottom have those portions of the tie rods which are attached to the sidewalls mounted in a substantially straight line extending from the sidewall attaching point to its retention with a hold-down plate.

7. A tie rod apparatus for retaining the sidewalls as in claim 6 in which the hold-down plate is disposed above and in engagement with the tie rod.

8. A tie rod apparatus for retaining the sidewalls as in claim 6 in which the structure is a four sided pool and there are at least two tie rods each passing below the hopper and with the planes in which the tie rods are disposed being arranged to intersect at substantially right angles to each other, one tie rod passing the other while each is restrained by a common hold-down plate against upward lifting.

9. A tie rod apparatus for retaining the sidewalls as in claim 8 in which the tie rods extending the length of the swimming pool and passing through the hopper portion has intermediate its length and adjacent the hopper portion a support plate adapted to engage and support the tie rod against downward movement and provide a support for one end of a downwardly directed portion of the tie rod.

10. A tie rod apparatus for retaining the sidewalls as in claim 5 in which the structure has the sidewalls arranged in a generally rectangular pattern with a hopper arranged toward one end, and with those tie rods extending from the sidewalls and laying in a plane common to the hopper having the rods directed downwardly from the sidewalls to the hold-down plate at an angle of 30 to 45 degrees.

11. A tie rod apparatus for retaining sidewalls as in claim 5 in which the water retaining structure is a canal-like structure whose bottom is deepened to provide a regular channel of determined depth and in which the sidewalls are restrained by a plurality of tie rods each attached to at least one hold-down plate at substantially the lowermost channel portion below which the attached tie rod passes.

12. A tie rod apparatus for retaining the sidewalls as in claim 5 of a structure such as a swimming pool in which the contoured bottom has at least one tie rod arranged to pass below said contoured bottom and in which intermediate one downwardly directed tie rod portion there is attached a second hold-down plate at a level above the lowermost hold-down plate. 

1. A system for retaining the sidewalls of a swimming pool and the like against the outward thrust of contained water of a determined depth in the pool in which the restraining is by members such as tie rods, straps and the like, said restraining members extending from one sidewall to an opposite sidewall and below a liner member forming at least the water retaining means for the bottom of the pool distinguished by having at least a depressed area, said system including: (a) at least one restraining member extending from one sidewall to an opposite sidewall and below at least a portion of the bottom which has been contoured to extend downwardly below the sidewalls to form a hopper, trough, channel and the like, said restraining member being below the liner and at no less than the contoured bottom surface, and (b) at least one hold-down plate secured to the restraining member at substantially its lowermost point, said hold-down plate being made a determined size and oriented so that the weight of the water in the pool and above said plate is utilized to maintain the plate and the restraining member in its installed condition and against the upwardly resultant forces developed in the retaining member as it retains the sidewalls against outward thrust.
 1. A system for retaining the sidewalls of a swimming pool and the like against the outward thrust of contained water of a determined depth in the pool in which the restraining is by members such as tie rods, straps and the like, said restraining members extending from one sidewall to an opposite sidewall and below a liner member forming at least the water retaining means for the bottom of the pool distinguished by having at least a depressed area, said system including: (a) at least one restraining member extending from one sidewall to an opposite sidewall and below at least a portion of the bottom which has been contoured to extend downwardly below the sidewalls to form a hopper, trough, channel and the like, said restraining member being below the liner and at no less than the contoured bottom surface, and (b) at least one hold-down plate secured to the restraining member at substantially its lowermost point, said hold-down plate being made a determined size and oriented so that the weight of the water in the pool and above said plate is utilized to maintain the plate and the restraining member in its installed condition and against the upwardly resultant forces developed in the retaining member as it retains the sidewalls against outward thrust.
 2. A system for restraining the opposite sidewalls of a pool as in claim 1 in which said pool is formed with at least two substantially straight opposite sidewalls and the bottom is formed with a hopper and with at least one of the restraining members extending across the pool at and below the liner supporting surface of said contoured hopper with each of attaching lengths of said restrAining member being directed downwardly in a substantially straight line from the sidewalls of the pool to its engagement with the hold-down plate.
 3. A system for restraining the opposite sidewalls of a pool as in claim 2 in which the hold-down plate is disposed above and in engagement with the lowermost portion of the restraining member.
 4. A system for restraining the opposite sidewalls of a pool as in claim 2 in which the pool has four sides and there are at least two restraining members each passing below the hopper and with the planes of each restraining member being disposed at substantially ninety degrees to each other, each member being retained by the same hold-down plate against upward lifting.
 5. A tie rod apparatus for retaining the sidewalls of a water retaining structure such as swimming pools, canals and the like, said structures having a contoured bottom extending at least in part below the sidewalls and disposed to support a flexible liner for retaining the water in the structure, said system including: (a) at least one tie rod attached to and extending from one substantially straight sidewall to an opposite straight sidewall, said tie rod laying in a plane which is substantially normal to the top surface of the water when in the structure, said tie rod directed downwardly from both sidewalls and arranged to lay below the flexible liner and the contour of the bottom on which the liner rests, and (b) at least one hold-down plate secured to said tie rod at substantially its lowermost point, said hold-down plate being made of a determined size and oriented so that the weight of the water in the pool and on said liner above said plate is utilized to maintain said plate and the tie rod in its installed condition and against the upwardly resultant forces developed in the tie rod as it retains the sidewalls against the outward thrust load of water against the sidewalls.
 6. A tie rod apparatus for restraining sidewalls as in claim 5 in which those tie rods extending from one sidewall to an opposite sidewall and which lay in a plane passing through a depressed area in the bottom have those portions of the tie rods which are attached to the sidewalls mounted in a substantially straight line extending from the sidewall attaching point to its retention with a hold-down plate.
 7. A tie rod apparatus for retaining the sidewalls as in claim 6 in which the hold-down plate is disposed above and in engagement with the tie rod.
 8. A tie rod apparatus for retaining the sidewalls as in claim 6 in which the structure is a four sided pool and there are at least two tie rods each passing below the hopper and with the planes in which the tie rods are disposed being arranged to intersect at substantially right angles to each other, one tie rod passing the other while each is restrained by a common hold-down plate against upward lifting.
 9. A tie rod apparatus for retaining the sidewalls as in claim 8 in which the tie rods extending the length of the swimming pool and passing through the hopper portion has intermediate its length and adjacent the hopper portion a support plate adapted to engage and support the tie rod against downward movement and provide a support for one end of a downwardly directed portion of the tie rod.
 10. A tie rod apparatus for retaining the sidewalls as in claim 5 in which the structure has the sidewalls arranged in a generally rectangular pattern with a hopper arranged toward one end, and with those tie rods extending from the sidewalls and laying in a plane common to the hopper having the rods directed downwardly from the sidewalls to the hold-down plate at an angle of 30 to 45 degrees.
 11. A tie rod apparatus for retaining sidewalls as in claim 5 in which the water retaining structure is a canal-like structure whose bottom is deepened to provide a regular channel of determined depth and in which the sidewalls are restrained by a plurality of tie rods each attached to at least one hold-down plate at substantially the Lowermost channel portion below which the attached tie rod passes. 